Protective insert for hydraulic presses and article and method used in the manufacture thereof

ABSTRACT

A protective insert adapted to engage a flexible wall of a pressurized chamber of a hydraulic press, with the insert being situated between this flexible wall and a punch around which a sheet metal workpiece is shaped. The protective insert has at least a pair of elastic flexible sheets firmly fixed to each other at a central region thereof, these sheets having portions surrounding their central connected portions and separated from each other, for instance, by a layer of lubricant. The central region holds the sheets together in the required relationship one with respect to the other. During the manufacture of the insert there is initially located between the sheets of the insert a metallic separator formed with a central opening through which the central portions of the elastic sheets are united as by being vulcanized to each other. Then one of these sheets is cut through at the region of the periphery of the separator so that the latter can then be removed.

United States Patent [72] Inventors Jarmlav Bur-ck 3,353,388 ll/l967 Schultz et al. 72/63 Prague; 3,430,473 3/1969 Edwards 72/63 E ovsky Nmbod m Primary Examiner-Richard J. Herbst Attorney-Richard Low [211 App]. No. 792,333 [22] Filed Jan. 21, 1969 patfimed June 1971 ABSTRACT: A protective insert adapted to engage a flexible Asslgnee "Ylkum mwmvych made wall of a pressurized chamber of a hydraulic press, with the inmicmhodolkh sert being situated between this flexible wall and a punch around which a sheet metal workpiece is shaped. The protecv tive insert has at least a pair of elastic flexible sheets firmly [54] PROTECTIVE INSERT FOR HYDRAULIC PRESSES to eaeh other at adeenglal regronathereof, these sheets AND ARTICLE AND METHOD USED IN THE avrng portions surroun mg err centr connected portions and separated from each other, for instance, by a layer of MANUFACTURE THEREOF 2 Cum 6 Dnwing Figs lubricant. The central region holds the sheets together rn the required relationship one with respect to the other. During the U.S. manufacture of the insert there is located between the 321d 22/12 sheets of the insert a metallic separator formed with a central .1 opening the central ortions of the elastic sheets are united as by being vulcanized to each other. Then [56] References CM one of these sheets is cut through at the region of the UNITED STATES PATENTS periphery of the separator so that the latter can then be. 2,741,205 4/1956 Paulton 72/63 removed.

I I 1 3 2-- I l 4 L i ll /0 8 I i 9 1a i 7 I l Il a 1 PROTECTIVE INSERT FOR HYDRAULIC PRESSES AND ARTICLE AND METHOD USED IN THE MANUFACTURE THEREOF BACKGROUND OF THE INVENTION This invention relates to hydraulic presses.

More particularly, the present invention relates to that type of hydraulic press which is used for shaping metal sheets.

Presses of this type may be provided with a liquid-filled pressurized chamber having a flexible wall directed toward a punch of the press which is engaged by the metal workpiece so that during shaping of the latter the flexible wall of the pressurized chamber arranges itself around the punch.

In order to protect the wall of the pressurized chamber a protective insert is conventionally situated between this wall and the punch, and the present invention relates in particular to such a protective insert.

In conventional hydraulic presses of the referred to type, where the flexible wall of a pressurized chamber coacts with a rigid punch to shape the metal sheets, it is known to use elastic or resilient containers for the liquid, forming with the latter the pressurized chambers. These elastic or resilient containers are provided with a protective insert which bears against the metal sheet during the shaping thereof. As the rigid punch penetrates into the pressurized chamber so that the latter arranges itself around the punch during the shaping of the metal, the protective insert is designed in such a way as to assure a perfect and precise contact between the metal sheet and the punch, guaranteeing precise shaping of the workpiece, while at the same time protecting the pressurized chamber.

In view of these considerations, it is essential that the protective insert have considerable elasticity, particularly in a radial direction, so as to be capable of withstanding the relatively high mechanical stresses to which such an insert is subjected, in combination with a low coefficient of friction between the insert and the metal sheet so that the protective insert will not in any way work against the proper shaping of the metal sheet. In order to render such protective inserts highly resilient, the cross sections thereof have been modified in various ways, as, for example, in such a way that the circumferential portion of such an insert is thinner than the remainder thereof.

Nevertheless, inserts of this type require special reinforcing elements to support their edges. Furthermore, various means are essential to assure an operation where the edge of the protective insert will bear reliably against the flexible wall of the pressurized chamber even in the pressure-free condition of the components when no operations are taking place. For this latter purpose various retaining and supporting elements have been utilized up to the present time, with such components being secured or loosely located within the pressurized chamber.

According to other known arrangements, the protective insert is associated with a metallic ring secured thereto as by vulcanization.

All of these various known constructions of the protective inserts result in complicated structures undesirably increasing the costs without actually providing any insert which can operate efficiently over a long period of time so that it becomes possible to change one insert for another only after a relatively large number of workpieces have been shaped.

SUMMARY OF THE INVENTION It is accordingly a primary object of the present invention to provide an insert which will avoid the above drawbacks.

It is also an object of the invention to provide a method for manufacturing such a protective insert.

Furthermore, it is an object of the invention to provide an article to be used in the manufacture of the insert.

An additional object of the invention is to provide an insert of the above referred to type which is simple in its construction and inexpensive to manufacture.

Also, it is an object of the invention to provide a protective insert which, without using any additional means, can be properly arranged to coact with the pressurized chamber of the hydraulic press.

Still further, it is an object of the invention to provide an insert which will be subjected to a minimum extent of mechanical stressing.

Thus, it is an object of the invention to provide a protective insert which will have a longer lifetime of reliable operation enabling a large number of workpieces to be shaped while using the same protective insert of the invention.

According to the invention, the protective insert is composed of at least two elastic flexible sheets having central regions fixedly connected and united to each other and having separate regions surrounding the interconnected central regions so that these separate regions of the sheets can move with respect to each other. A suitable layer of lubricant can be located between the separate sheet regions of the protective insert. The interconnected central portions thereof reliably hold these sheets in their proper operative positions with respect to each other.

The article which can be used in the manufacture of such an insert includes the pair of layers of flexible elastic sheet material which have situated between themselves a separator sheet formed with a central opening through which the central regions of the elastic sheets can be bonded to each other. Thereafter the separator sheet is removed so that the portions of the elastic sheets surrounding their interconnected portion will remain separate from each other.

Thus, according to the method of the invention, the pair of elastic flexible sheets are initially placed one next to the other with the separator sheet situated therebetween, and the central regions of these elastic sheets are joined to each other through the central opening of g the separator sheet. Thereafter, one of the elastic sheets is cut through to the region of the periphery of the separator sheet so as to have access to the latter, thus facilitating removal of the separator sheet to achieve the protective insert of the invention.

BRIEF DESCRIPTION OF THE DRAWING The invention is illustrated by way of example in the accompanying drawing which forms a part of this application and in which:

FIG. I is a schematic fragmentary, partly sectional, elevation of a hydraulic press provided with the protective insert of the invention;

FIG. 2 is a transverse sectional elevation of the protective insert of the invention, shown during a stage in the manufacture thereof;

FIG. 3 shows the protective insert of the invention also at a stage during the manufacture thereof, the embodiment of FIG. 3 being different from that of FIG. 2;

FIG. 4 is a transverse sectional elevation of the separator sheet used in the manufacture of the protective insert of the invention;

FIG. 5 is a top plan view of the separator sheet; and

FIG. 6 is a fragmentary transverse section of the separator sheet at an enlarged scale, showing the configuration of grooves formed in a surface of the separator.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawing in greater detail, and initially to FIG. I, the hydraulic press which is schematically and fragmentarily illustrated therein to an extent sufficient to afford a full understanding of the present invention has an upper body 1 of hollow cylindrical configuration. A cylindrical ram 2 is adapted to axially reciprocate within the upper cylindrical body 1. The ram 2 is secured to a frame 3 of the press, the frame 3 being actuated in a known manner through suitable hydraulically driven gears or other power means. The upper cylindrical body I is adapted to slide vertically with respect to the frame 3 on a plurality of pilot pins 4 which are fixed to and extend downwardly from the frame 3 and are uniformly distributed about the cylindrical body 1, extending freely through openings 5 formed in a flange b of the body 1. Only one of the guide pins 4 and only a part of the flange 6 are illustrated at the upper right portion of FIG. 1. The pin 4 has a head 5' at its lower end to limit the extent of movement of the components 1 and 3 away from each other.

Within the hollow interior of the cylindrical body I, there is a pressurized chamber 7 formed by a container 7 having a wall of elastic flexible sheet material. The container 7 is fixedly connected with the lower end face of the ram 2 by way of a clamping plate b which is itself secured to the ram by way of the screws 9. in order to prevent the elastic wall of the container 7 from penetrating into any gap remaining between the exterior surface of the ram 2 and the interior surface of the cylindrical body 1, a spacer ring 10 is situated at the inner surface of the body 1 against the outer peripheral edge portion of the downwardly directed face of the ram 2.

The lower part of the elastic container 7 has situated against its flexible wall the protective insert 11 of the invention. Of course, the interior of the container 7 is filled with a pressure medium such as liquid, and it is the wall of the container 7 which is to be protected by the insert 11. This insert 11 is simply in contact with the lower wall of the container 7 which defines the pressurized chamber 7 and is not in any way fixed thereto.

In order to reliably retain the protective insert 11 in its position bearing against the flexible elastic wall of the container '7, a metallic retaining ring 12 is situated against an upwardly directed shoulder 13 in the insert 11. This metallic retaining ring forms a spacer which engages the outer periphery of the insert 11 to retain the latter within the cylindrical body 1 and to prevent any part of the insert 11 from penetrating into any gap between the shoulder 13 and a thrust ring 15 which is adapted to be received in the cylindrical body 1 at the lower region thereof.

This thrust ring 15 is mounted upon a lower stationary press body 14. A punch 16 is adapted to extend upwardly and to pass freely through a central opening of the ring 15. The punch 16 is raised hydraulically through a suitable transmission gearing or the like of the press, the structure which drives the punch 16 being situated in the lower body M of the press not being illustrated since it is well known and forms no part of the invention.

The protective insert 11 is of a dished configuration (see FIGS. 2 and 3) and includes, in the illustrated example, a pair of layers 17 and 18 made of elastic flexible sheet material, preferably of plastic sheets of different hardness. The lower sheet 17 which engages directly a sheet metal workpiece 25 during shaping of the latter (see FIG. 1) is made of the harder material since it also serves, during the pressing and shaping operations, to hold a peripheral flange of the worksheet 25 in engagement with the thrust ring 15. During the upward movement of the punch 16 into the pressurized chamber 7 while the lower wall of the container 7 arranges itself automatically about the punch 16 pressure is transmitted through the protective insert 11 so as to precisely shape the workpiece 25 to the configuration of the punch 16.

On the other hand, the upper layer 1% of elastic flexible sheet material is of lesser hardness and in fact of greater elasticity. It has a central region 19 fixedly connected with a central region of the layer 17 so as to form an inseparable union therewith. Prior to the final finishing of the protective insert 11, with such final finishing including operations such as pressing or vulcanizing the sheet material layers 17 and 18 to each other, there is situated, according to the invention, a separator sheet 20 between the layers 17 and 18. This separator sheet 211 is made of a thin metal sheet and is suitably shaped so as to have the dished configuration apparent from F16. d. The separator sheet 20 is of circular configuration and is formed with a central opening 21, as is apparent from F IG. 5. The presence of the opening 21 enables the sheets 17 and 18 to be united to each other at their central regions through the opening 21. in such a manner that for all practical purposes the sheets 17 and 18 are integral at their central regions. Thus, during the finishing of the protective insert 11, the layers 17 and 18 are permanently secured to each other at the central regions thereof, which engage each other through the opening 21 of the separator sheet 20. As a result of this bond between the elastic flexible sheets 17 and 18, the sheets are reliably maintained in their proper operative positions with respect to each other, and proper positioning of the central region of the harder lower sheet 17 relative to its peripheral region is assured.

it is to be noted that the sheets 17 and 1h extend outwardly beyond the outer periphery of the separator sheet 211 and that during the finishing operations when the sheets are vulcanized to each other they will be vulcanized also at their outer peripheral regions where they extend beyond the periphery of the sheet 21). Due to the configuration of the separator sheet 211 and the sheets 17 and 18, the sheets 20, 17 and 18 assume during the pressing and uniting of the sheets 17 and 18 to each other the dished form apparent from FIGS. 2 and 3.

After the protective insert 11 has been finished, as has been described, a cut 23 is made through the lower sheet 17 along and in the region of the periphery of the separator sheet 211 (see FlG. 2). This cut extends perpendicularly with respect to the outer flat bottom surface of the sheet 17. However, as is indicated in H0. 3, instead of providing an endless cut 23 as shown in FIG. 2, it is also possible to provide through the lower sheet 17 an endless cut 24 of frustoconical configuration, also extending along the outer periphery of the separator 20 and having its largest diameter situated at the exterior flat bottom surface of the sheet 17.

lo order to provide either the cylindrical cut 23 or the frustoconical cut 24, the insert is clamped in a rotary chuck of a machine tool, such as a lathe, and a suitable sharp tool is used to cut through the sheet 17.

In this way access may be had to the separator sheet 211 since after being provided with the endless cut 23 or 24, the sheet 17 can be flexed away from the sheet 18 at the region where the separator sheet 20 is located. Then the separator sheet 20 is cut with a suitable tool, for instance, in half so that it can very easily be removed from between the sheets 17 and 1b. in order to facilitate the removal of the separator sheet 20 it can be provided in one face with a plurality of radially extending grooves 22 of V-shaped cross section (see FIG. 6). These grooves form in the sheet 20 weakened regions where the sheet can easily come apart to facilitate removal from between the sheets 17 and 1%.

After the separator 20 has thus been removed, a suitable lubricant is situated between the layers 17 and 18.

It is thus apparent that the protective insert 11 is simple and inexpensive to manufacture and does not require any additional means to properly arrange it within the body 1 to engage the bottom wall of the container 7 which defines the pressurized chamber 7. During pressing operations the layers 17 and 18 will be subjected to minimum mechanical stresses inasmuch as the portion of the layer 17, which surrounds its central region that is directly bonded to the layer 18, is free to move relative to the remaining structure including the outer periphery of the layer 17. As a result, the protective insert of the invention will have a long operating life, enabling a large number of metal sheets, such as workpieces 25, to be formed before it becomes necessary to exchange one protective insert for another.

We claim:

1. For use in a hydraulic press having a pressurized chamber defined by an elastic flexible container, filled with a liquid medium, and adapted to yield with respect to a punch during shaping of a sheet metal workpiece by the punch, a protective insert situated between the punch and a flexible portion of the container wall, which is directed toward the punch for protecting said wall portion, and for directly engaging the metal workpiece during the shaping thereof, said protective insert comprising at least two layers of flexible sheet material having workpiece.

2. The combination of claim 1 and wherein a lubricant is situated between the separate regions which surround the united central regions. 

1. For use in a hydraulic press having a pressurized chamber defined by an elastic flexible container, filled with a liquid medium, and adapted to yield with respect to a punch during shaping of a sheet metal workpiece by the punch, a protective insert situated between the punch and a flexible portion of the container wall, which is directed toward the punch for protecting said wall portion, and for directly engaging the metal workpiece during the shaping thereof, said protective insert comprising at least two layers of flexible sheet material having central regions directly and fixedly connected to each other and regions surrounding said central regions and being separate from each other, so that the union of said central regions of said insert maintains said layers properly connected to each other while beyond the united central regions the layers can shift with respect to each other during shaping of the workpiece.
 2. The combination of claim 1 and wherein a lubricant is situated between the separate regions which surround the united central regions. 